Check that each output's directory exists and is writable.
The write permission itself is not tested — creating and removing a file on
every run would be surprising for an output directory. This catches the two
causes that actually occur: a missing directory, and one the process cannot
write to.
Check that each output's directory exists and is writable.
The write permission itself is not tested — creating and removing a file on every run would be surprising for an output directory. This catches the two causes that actually occur: a missing directory, and one the process cannot write to.